Pneumatic rubber tires are conventionally prepared with a rubber tread and an underlying supporting carcass for the tread. The carcass is conventionally composed of one or more rubberized cord reinforced plies. The tire may also contain a circumferential cord reinforced belt positioned between the tread and carcass plies. Such ply and belt construction for a pneumatic tire are well known to those having skill in such art.
Such carcass plies and circumferential belts are historically composed of polymeric or metallic cords (which are continuous in nature and not individual discrete fibers) which are encapsulated with a rubber composition. Such rubber composition is typically reinforced with particulate carbon black and perhaps, in come cases, also a particulate silica.
However, aircraft tires are subject to substantial distortative forces upon associated aircraft landing and taking off procedures where the tire may be required to suddenly accelerate from zero to 200 miles per hour or greater under a significant load.
Accordingly for aircraft tires which may have a carcass composed of from one to 20, or greater, and more conventionally from 4 to 16, carcass plies, each ply being composed of rubber encapsulated cords, the rubber composition is of a special consideration because an aircraft tire represents a relatively large heat sink where heat is generated resulting in a potentially large increase in operating temperature over a relatively short time frame due to expected large loads placed upon the tires during aircraft landings and takeoffs at high speeds in which such tires experience relatively large deflections. Of special concern for such tires are attained and retained physical properties such as low hysteresis (to promote low heat generation during dynamic use of the tire due to relatively large and sudden loads experienced, for example, by aircraft takeoffs and landings), as well as tensile strength.
Thus dissipation of heat from such an aircraft tire under such operating condition is a challenge in order to maintain such physical properties.
Historically, in U.S. Pat. No. 5,396,940 a carcass ply rubber composition is related which is composed of 5 to 95 phr of epoxidized natural rubber, 5 to 85 phr of silica, a silica coupler, carbon black which can be a carbon black such as N299, which can also contain 95 to 5 phr of other rubbers including natural rubber and cis 1,4-polybutadiene rubber. In U.S. Pat. No. 6,022,326, a tire is related which has a carcass ply component having a rubber composition reinforced with carbon black to the exclusion of silica.
In the description of this invention, the term “phr” where used means “parts of material by weight per 100 parts by weight of rubber”. The terms “rubber” and “elastomer” are used interchangeably unless otherwise mentioned.